1. Field of the Invention
The present invention relates to a method of ultrasonically micro machining a workpiece with a diamond faced patterned die, and more particularly, to micro machining air bearing surfaces of magnetic head sliders with a complex pattern to control flying height of each slider above a spinning magnetic disk.
2. Description of the Related Art
In magnetic disk media drives, inductive thin film magnetic heads are :normally used for implementing read/write functions. When a disk is rotated, a surface of the disk carries a thin film of air ("air bearing") which supports a slider on which a magnetic head is mounted at some height ("flying height") above the surface. The flying height depends upon the configuration of the slider. It is desirable that the flying height be as low as possible. The lower the flying height, the greater the amount of data stored per unit area of the disk surface.
In order to lower the flying height, sliders are typically configured with two or more rails. These rails are formed by machining the air bearing surface of the slider with one or more grinding wheels. One problem with this machining process is that the grinding wheel chips portions of the slider which are outside of the intended grinding area. Another problem is that the heat generated during the grinding process can cause stress of the ceramic slider material. This chipping and/or stress of the slider material can affect the magnetic head's reading and writing functions as well as its flying height. Another problem with machining is that the grinding wheel is capable of only machining straight patterns into the slider air bearing surface. It has recently been found that more complex patterns in the air bearing surface of a slider result in a lower flying height than that obtainable by two or more rails.
In order to obtain a complex slider air bearing pattern, sliders have been machined by using a reactive ion etching process. With this process, a magnetic head slider can be machined to any desired shaped pattern. A problem with the reactive ion etching process, however, has been the inability to obtain sheer walls in the pattern, namely, walls which are true to form and perpendicular to the flying surface of the slider. The reactive ion etching process typically results in the sloping (non-perpendicular) walls taking on a sloping configuration. Sloping walls make it very difficult to control the final desired pattern of the slider air bearing surface. This is especially true when the air bearing surface is lapped after the pattern is formed. Other problems with the reactive ion etching process are that it is time-consuming, requires a clean room, has many process steps, uses extensive amounts of chemicals, creates redeposition on the workpiece, produces corrosive byproducts, creates particulate contaminants, and requires expensive capital equipment and maintenance. Neither the grinding wheel process or the reactive ion etching process is conducive to mass machining magnetic head sliders nor are they conducive to reproducible products from one production run to the next.